30. ---They are quiet, aren’t they? ---Yes. They are accustomed _____ at meals.
____is certain is ___prevention is more important than treatment .
_______has recently been done to provide more buses for the people ,a shortage of public vehicles remains a serious problem .
The experience of the Chinese nation attests to a truth____ a nation loses in times of disaster will be made up for by her progress
In his speech, Premier Wen Jiabao points out that creativity is ______it takes to keep a nation highly competitive .
The book is meant to ________needs it .